Defrost means for air conditioning apparatus



Nov. 20, 1962 w. w. WEISS 3,064,443

DEFROST MEANS FOR AIR CONDITIONING APPARATUS Filed Sept. 16. 1959 2 Sheets-Sheet l INVENTOR. FIG. l/a/fcr M 11/42/55 W. W. WEISS Nov. 20, 1962 DEF'ROST MEANS FOR AIR CONDITIONING APPARATUS 2 Sheets-Sheet 2 Filed Sept. 16, 1959 FIG. 2

INVENTOR. Ma/fer [d [(fezlss 414 United States Patent ()fiice 3,964,443 Patented Nov. 20, 1952 3,064,443 DEFROST MEANS FOR AIR CONDITIONING APPARATUS Walter W. Weiss, Tonawanda, N.Y., assignor to Fedders Corporation, Maspeth, N.Y. Filed Sept. 16, 1959, Ser. No. 840,403 2 Claims. (Cl. 62-156) This invention relates to defrosting devices for refrigeration systems such as used in air conditioning units.

In the operation of air conditioning units humidity and temperature conditions are frequently encountered where the evaporator coil is subjected to rapid frosting and subsequent icing resulting in the functional failure of the system. Various control devices have been used for alleviating this condition by shutting down the compressor in response to coil temperatures in order to permit melting of the frost and ice before restoration of operation. In common, such control devices have failed periodically because of their inability to cope with recurrent violent frosting conditions, where partial defrosting is followed by solid freezing in rapid order and as a result an undesirable cyclic or hunting condition of operation of the system is encountered. This condition, aside from placing undesired loads on the compressor, rendered the unit ineffectual for long periods of time.

in the present invention a compressor control instrumentally is provided which is not only immediately sensitive to humidity conditions but is also capable of rendering the system inoperative until the condition of the evaporator coil warrants a resumption of the cycle to the end that objectionable cycling is totally eliminated. Other features of the invention reside in the advantages of an extremely simple structure of the control and to flexibility of operation under various conditions as will be better understood by reference to the accompanying specification and drawing wherein:

FIG. 1 is a diagrammatic view of the elements of an air conditioning unit showing the application of the control of the invention to the system. The evaporator and the accompanying water trap of the invention are shown in end elevation and in non diagrammatic form.

FIG. 2 is a top view of an air conditioning unit with portions broken away to show the evaporator.

FIG. 3 is a front view of the unit with the front panel removed.

FIG. 4 is a perspective view showing the water trap of the defrosting control.

In the drawings FIGS. 2 and 3 show an air conditioning unit of the window mounted type having a typical refrigeration system installed therein consisting of a motor driven compressor 11, an outside coil or condenser 12, a finned inside coil or evaporator 13, and air moving elements consisting of a blower 14 and a coaxial fan 15 for circulating air through the evaporator 13 and condenser 12 respectively, as indicated by arrows in FIG. 2. A motor 16 serves as a common drive for the blower 14 and fan 15. The refrigerant circuit is diagrammatically shown in FIG. 1 where it will be observed that the compressor 11 supplies refrigerant to the condenser 12, through a pipe 17, and the cooled refrigerant is then directed to the evaporator 13 via a pipe 18 in which is interposed a suitable control device, such as a capillary tube 19. Refrigerant is delivered from the evaporator 13 to the suction side of the compressor through a pipe 21 to complete the circuit.

In the electrical end of the system, a power source 22, 23, is connected to the motor junctions 24, 25, of the compressor 11 through lines 26 and 27. Similar switches S and S are interposed in the lines 26 and 27 respectively, and such switches are preferable of the temperature responsive type, having a hermitically charged system including a thermostatic tail 30 and a moveable bellows 31 for operating a switch 32 and thus controlling the operation of the power source to the compressor motor.

The switch S will be recognized as the familar room temperature control element which opens or closes the compressor motor circuit in response to temperature conditions in the room. In the present case the tail 30 of the switch S is disposed in the path of the air entering the blower 14 and thus it responds to the inlet air temperature. The remaining switch S similarly controls the operation of the compressor, but in response to frosting conditions in the evaporator 13 through instrumentalities forming the invention which will now be described.

A small stamping 33 is formed with a hook terminal 34 which is engaged on one of the loops 13a of the evaporator 13 for support, and its lower terminal consists of an angular and pointed trough 35, which is disposed directly over an open vial or water trap 36. Both the stamping 33 and trap 36 may be soldered to suitable loops 13a of the evaporator to retain them in Vertical alignment. The end of the tail 30 of the switch S is disposed within the vial 36. It will be observed that water condensing on the loops and adjoining surfaces of the evaporator in the locale of the described elements 33 and 36 will be directed into the vial and in contact with the tail 30 of the switch 8'.

In the operation of the system when humidity conditions are normal, evaporator coil temperatures are typically above 35 F. and air to be cooled passes freely through the evaporator until it is sufficiently cooled say to 70 F. to cause the circuit opening operation of the switch S in cyclic fashion. The remaining switch 8' is set to open at temperatures below 32, and thus, during normal operation of the system is closed, regardless of thepresence of water in the vial 36. During abnormal operation of the system, that is, when humidity conditions are severe, the surfaces of the evaporator 13 will become encased in frost until air circulation is partially or totally blocked. Under these conditions the coil temperature drops rapidly and the Water in the vial 36 is cooled until freezing occurs, whereupon, the switch S is caused to open the circuit of the compressor and thus shut down the system until the ice has melted in the vial 36 and the temperature of the water therein is raised to above 32 F.

It will be understood that the time factor encountered in the melting of the ice in the vial 36 is highly significant, as it parallels the time required to melt the ice on the surfaces of the evaporator 13. Thus before the operation of the system is caused to be resumed by actuation of the switch S in response to the temperature of the water in the vial 36, it, may reasonably be assumed that ice and frost formation has disappeared from the evaporator 13. The restored system will thus run normally for an appreciable length of time until the same conditions will cause its cessation in another defrosting cycle. The invention thus assures that rapid off and on operation of the system as the result of partial melting of the ice is efiectually prevented.

I claim:

1. The combination with an air conditioning unit having a refrigerant circuit including a motor driven compressor, an outside coil, an inside coil, an air circulating system for each coil, and temperature responsive means in the inside coil air circulating system for controlling the operation of the compressor, of a water collecting vial secured in intimate contact with said inside coil, and a second temperature responsive means responding to freezing temperature of the water in said vial for rendering said refrigeration circuit inoperative.

2. The combination with an air conditioning unit having a refrigerant circuit including a motor driven compressor, an outside coil, an inside coil, an air circulating system for each coil, and temperature responsive means in the inside coil air circulating system for controlling the operation of the compressor, of an open water collecting vial secured in a vertical position to said inside coil, a trough disposed in close proximity to said inside coil and above said vial for directing waters of condensation from said inside coil into said vial, and a second temperature responsive means having a thermostatic tail disposed in said vial, said last temperature responsive means responding to freezing temperature of water'in said vial for rendering said refrigeration circuit inoperative.

References Citedin the file of this patent UNITED STATES PATENTS Pick July 6, 1937 Philipp Nov. 29, 1938 Crago Ian. 10, 1939 Winther Mar. 19, 1940 Jones Ian. 19, 1954 Tillman Dec. 11, 1956 MeGrath Dec. 22, 1959 

